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authorMartin K. Petersen <martin.petersen@oracle.com>2009-12-03 09:24:48 +0100
committerJens Axboe <jens.axboe@oracle.com>2009-12-03 09:24:48 +0100
commit98262f2762f0067375f83824d81ea929e37e6bfe (patch)
treea26618d5c305eed975501c80cb02bc0f1b6e4524 /block/blk-settings.c
parent464191c65b85a8ec68a6e1a6293af625287c807e (diff)
downloadlinux-2.6.34-ux500-98262f2762f0067375f83824d81ea929e37e6bfe.tar.gz
block: Allow devices to indicate whether discarded blocks are zeroed
The discard ioctl is used by mkfs utilities to clear a block device prior to putting metadata down. However, not all devices return zeroed blocks after a discard. Some drives return stale data, potentially containing old superblocks. It is therefore important to know whether discarded blocks are properly zeroed. Both ATA and SCSI drives have configuration bits that indicate whether zeroes are returned after a discard operation. Implement a block level interface that allows this information to be bubbled up the stack and queried via a new block device ioctl. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block/blk-settings.c')
-rw-r--r--block/blk-settings.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 1ebc1fdb914..dd1f1e0e196 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -101,6 +101,7 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->discard_granularity = 0;
lim->discard_alignment = 0;
lim->discard_misaligned = 0;
+ lim->discard_zeroes_data = -1;
lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
lim->alignment_offset = 0;
@@ -544,6 +545,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
t->io_min = max(t->io_min, b->io_min);
t->no_cluster |= b->no_cluster;
+ t->discard_zeroes_data &= b->discard_zeroes_data;
/* Bottom device offset aligned? */
if (offset &&